Fixed frequency source timing processor method and apparatus

Abstract

The decoder method and apparatus receives an information stream comprising timing information and respective payload information. A substantially fixed frequency source is used to generate local timing information, which is used to decode the payload information. A difference signal representing the timing difference between the local timing reference and the received timing information is calculated and used to adjust the decoded payload information signal.

What is claimed is:  
     
       1. A method of processing an information stream comprising remote timing information and respective payload information including video information comprising viewable and non-viewable horizontal video lines, said method comprising the steps of: 
       generating local timing information utilizing a fixed frequency source;  
       calculating a difference between said remote timing information and said local timing information;  
       decoding said payload information using said local timing information signal to produce decoded payload information; and  
       correction timing errors by selectively increasing or decreasing the duration of non-viewable horizontal video lines.  
     
     
       2. The method of claim  1  wherein: 
       said non-viewable horizontal video lines comprise horizontal video lines occurring during a vertical blanking interval said selective increase or decrease in duration of said horizontal video lines causing a corresponding increase or decrease in said vertical blanking interval.  
     
     
       3. The method of claim  1  wherein said calculating step further comprises the step of filtering said difference. 
     
     
       4. The method of claim  1 , wherein said calculation is made using the time required for a vertical blanking interval the number of horizontal lines occurring within the vertical blanking interval, and the total amount of time to be added or subtracted from a frame or field to correct a timing error. 
     
     
       5. Apparatus for processing an information stream comprising remote timing information and respective payload information comprising video information comprising viewable and non-viewable horizontal video lines, said apparatus comprising: 
       a source of a fixed frequency signal,  
       a subtractor coupled to said fixed frequency source, and responsive to said fixed frequency signal and said remote timing information, for producing a difference signal;  
       a correction calculator coupled to said subtractor, and responsive to said difference signal, for producing at least horizontal synchronizing signals compatible with a payload information decoder, said correction calculator correcting timing errors by selectively increasing or decreasing the duration of horizontal synchronizing signals associated with non-viewable horizontal video lines.  
     
     
       6. The apparatus of claim  5  wherein said subtractor further comprises a an output filter for filtering said difference signal. 
     
     
       7. The apparatus of claim  5  wherein: 
       said horizontal lines occurring during a vertical blanking interval, said selective increase or decrease in duration of said horizontal lines causing a corresponding increase or decrease in said vertical blanking interval.  
     
     
       8. The apparatus of claim  5  wherein: 
       said calculation is made using the time required for a vertical blanking interval, the number of horizontal lines occurring within the vertical blanking interval, and the total amount of time to be added or subtracted from a frame or field.